Using olive and apple pomaces for fattening pig diets: Environmental impacts under an attributional and consequential perspective

The livestock sector plays an essential role in anthropogenic greenhouse gas emissions, where fodder crop production has been largely identified as the main contributor to their environmental impact. This research evaluates the attributional environmental impacts of introducing food industry subproducts such as apple and olive pomaces to reduce the proportion of maize grain in the formulation of diets for fattening pigs, according to four alternatives, including the current diet with 69% maize. For this, the life cycle assessment (LCA) methodology has been used to determine the hotspots associated to these changes, considering a cradle-to-gate approach and two functional units: 1kg of feed diet (FU1) and 1kg of weight gain (FU2). Furthermore, the potential environmental consequences of using these subproducts for pig diet have also been considered with a consequential LCA methodology. The results show that the best diet was the one containing about 33% maize and 43% subproducts for all categories analysed. In addition, the allocation method used to assign subproduct loads, including mass, economic zero-burdens allocation, is crucial to validate the assumptions and recommendations for this strategy. The consequential LCA results suggest that this strategy could involve both positive and negative impacts (considered as environmental credits), depending on the substitutes for the avoided maize stover and the potential displaced bioproducts that could be obtained from these subproducts, mainly for bioenergy production.